Subject: Re: [PATCH for-4.8_set4 0/2] Segment table support

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Wed, 13 Jul 2016 19:32:46 +0530

Benjamin Herrenschmidt <[email-masked]> writes:

> On Wed, 2016-07-13 at 15:10 +0530, Aneesh Kumar K.V wrote:
>> Hi,
>> 
>> This series add support for ISA 3.0 memory segment table.
>> 
>> Aneesh Kumar K.V (2):
>>   powerpc/mm: Switch user slb fault handling to translation enabled
>>   powerpc/mm: Support segment table for Power9
>
> The segment table will only be used for the nest MMU, shouldn't we keep
> that a separate path that we call explictly from fault interrupts
> coming from NestMMU agents instead ?
>

I haven't looked at the Nest MMU use of this. This patch is looking at
implementing the ISA 3.0 Segment table support for core. We determine
whether cpu will support this mode by looking at ibm,pa-features bit
value. If ibm,pa-features byte 40 bit 1 is not set, it indicates that
Segment table support is not there and hence we fallback to other MMU
mode supported by the CPU.

Going foward we may want to look at the possibility of having Nest use
segment table without core supporting them. But then that is not done as
a part of this patch.

-aneesh